Heat exchange structure



y 1955 I R. F. ADAMS 3,194,309

HEAT EXCHANGE STRUCTURE Original Filed July 16, 1954 v a Sheets-Sheet 1 FIG. I 2 F|s.3

J 771. ll 7/ 5 /a lb 16/ I2 INVENTOR:

BYW;

RICHARD F ADAM$ M QR A 770/? NEYS y 1965 R. F. ADAMS 3,194,309

HEAT EXCHANGE STRUCTURE I 7 Original Filed July 16, 1954 5 Sheets-Sheet 2 IN VEN TOR.

RICHARD F. ADAMS BY 1 g -86 ATTORNEYS July 13, 1965 R. F. ADAMS 3,194,309

HEAT EXCHANGE STRUCTURE 5 Sheets-Sheet 3 Original Filed July 16, 1954 INVENTOR. RICHARD F ADAMS BY I a ATTORNEYS 4 United Sttes Patent 0 3,1945% HEAT EXCHANGE STRUCTURE Richard F. Adams, Alton, lill., assignor to fllin Mathieson Chemical (Torporation, a corporation oi Virginia Original application July 16, 1954, Ser. No. 443,944, now Patent No. 2,944,328, dated .Fnly 12, 1960. Divided and this application Oct. 12, 1959, Ser. No. 848,387

4 Claims. (til. 165-170) This application is a division of copending application Serial No. 443,944, filed July 16, 1954, now U.S. Letters Patent No. 2,944,328 granted luly 12, 1960.

This invention relates to sheet metal hollow structures and more particularly to sheet metal heat exchange units having relatively thin walls.

A method of making hollow articles of sheet metal substantially free from solder or brazing materials and without the use of electric welding has been developed. By this method as practiced in the manufacture of refrigerator evaporators, for example, a weld preventing material is applied in a definite, foreshortened, and rather complex pattern between two weldable sheets of metal after which the sheets are fixed in super-position and hot rolled to form a single inflatable sheet. Upon inflation there is erected from and within the sheet a system of passag ways of predetermined dimensions and configuration. In this final passageway design it is frequently necessary to include a rather large cavity such as the header of a radiator or the boiler of a refrigerator evaporator. In the practice of-the above-noted method, it is a problem to make satisfactory large volume cavities of rather flat shape as distinguished from long narrow passageways inasmuch as the shert metal in the relatively thin walls of the extensive cavity or hollow is put to a greater pressure in tension than the walls of the narrow passageways; and, as a result, there is a tendency for the area around and including such headers or boilers to undergo excessive distortion or to burst.

To prevent distortion or bursting by high internal pressure, the prior art expedient of U.S. 1,712,085 (Litle) has been adapted to this method with only limited-success.

This involves application of a grid-like pattern which provides upon pressure welding a plurality of welded islands distributed throughout the boiler cavity. A serious disadvantage of this method of handling the prob- 1cm is that the etl'ective boiler volume is considerably reduced which necessitates provision of a larger area of boiler in the product than desirable and necessary. Another disadvantage is that the exterior of the boiler or accumulator is not smooth or substantially flat but is instead pock marked with a plurality of relatively steep walled depressions in which moisture and dirt will accumulate and from which the moisture and dirt are removable only with difficulty.

Therefore, one object of this invention is to provide a sheet metal heat exchanger unit pressure welding process having a large volume thin walled cavity. Another object to to providein such a unit a large volume cavity capable of holding a relatively flat shape with a minimum of distortion under internal inflation or operating pressure. Another object is to provide such a heat exchange unit having a relatively flat thin walled large volume cavity of increased strength for containing fluids under high pressure without bursting. Another object is to provide a heat exchange unit with internal elements for improving the heat transfer characteristics of the unit. Another object of this invention is to provide a new and improved internal structure of the sheet metal units to enable expansion with or without the use of press platens at very high pressures and to enable high operating pressures after expansion without rupturing the metal. It is till Patented july 13, 1965 still another object of this invention to provide a new and improved heat exchange unit. Further objects and advantages of this invention will become apparent from the following description which will be better understood with reference to the accompanying drawing, in which:

FZGURE l is a plan view illustrating one embodiment of the invention with a part broken away to better illustrate the structural details involved;

FIGURE 2 is an enlarged elevational cross-sectional view taken on line Illl of FIGURE 1;

FIGURE 3 is an elevational side view of the embodiment of FIGURE 1;

FIGURE 4 is a fragmentary perspective view with the sheets partially peeled and extended showing the structural details, manner of assembly and relationship of the component sheets used to make the hollow article of FIG- URE 1 in accordance with this invention prior to pressure welding by rolling and forming by inflation;

FIGURE 5 is a cross-sectional view taken on line V-V of FEGURE 4 through intermediate sheet 19;

FIGURE 6 is a plan view of a modification of the intermediate sheet structure.

In accordance with this invention there is provided a single sheet of metal embracing within the body of the metal intermediate the parallel or fiat faces thereof embryonic fluid passageways including a potential generally flat shaped cavity of rather large expanse which upon fluid inflation of the sheet develops a large volume recess the opposite walls of which are connected by a series of stay straps of sheet metal. Upon inflation of the single sheet there is provided in accordance with this invention a hollow sheet metal structure having a relatively flat thin walled voluminous cavity of large area relative to the sheet and with an internal sheet metal structure for reinforcing the cavity walls against excessive distortion or bursting which might be caused by the pressure of any fluid in the cavity. The internal sheet structure is adapted to adhere to the external walls :of the sheet alternately and is mechanically weakened to facilitate opening and expansion of the internal sheet to form internal straps.

To make the aforementioned new and improved hollow sheet metal units in accordance with the pressure welding method of this invention there is provided in the area of the desired boiler or header cavity a special new assembly of component layers of weldable sheets, including an expandable slitted or at least mechanically weakened interleaved sheet and weld preventing material, next this assembly is secured as a preliminary to welding to prevent relative slippage between layers and the assembly thus secured is subjected to .a single hot working as by rolling to a sufficient metal reduction to unite each of the outside sheet metal components at spaced points alternately with the interleaved sheet except where the elongated weld preventing material is interfacially continuously disposed. The special new assembly of components consists of at least two outer weldable sheets of metal, at least one intermediate sheet of weldable metal and at least between each of these outside sheet metal components and the adjacent intermediate sheet a layer of weld preventing material in a foreshortened grid-like open pattern. The periphery of each elongated pattern substantially coincides in superposition with the periphery of the internally reinforced extensive boiler or header cavity desired; but the so-called openings or islands of each pattern, at which welding between adjacent sheet metal components occurs, are staggered with respect to the openings of the adjacent pattern. By openings or islands of the grid pattern is meant the areas free from weld preventing material such as graphite.

leastand entirely across the area of the assembly where partial Welding is desired and where a boiler or header cavity is to be erected by inflation, one intermediate slitted,

.incisedor otherwise suitably weakened sheet of Welda-ble metal'to theopposite faces of which weld preventing mater'ial may be applied in a solid pattern except for a plurality of laterally and longitudinally spaced area's fr from weldpreventing material and which never overlap withthe weld-preventingmaterial-frce areas of the other sidev of the intermediate sheet. While it is preferred that the intermediate sheet be incised or slit between the spaced areas orpattern"openings free from Weld preventing material, the incisions need not extend entirely through the sheet. By incisions is meant any mechanical weakening' which will facilitate expansion of the intermediate sheetto form an open internal strap structure.

One pattern of weld preventing material. with spaced i islands free'fromsuch material may be applied to the inner face ofoneof the two outside component sheets of metal while the other, pattern is applied to the inner face of the other of the two outside sheets, instead of being applied to 'theintermediate sheet. In application of the patterns by either mode it is only necessary that the weldable islands of one pattern be offset from and not overlap with the islandsof the other, pattern. A regular pattern of spaced incisions or 'slitsthrough or nearly completely through the intermediate sheet or sheets permits .a larger over-all eX- pansion of the boiler, or header cavity and tends materially to reduce the lateral contraction anddistortion of-the fin- .is'hed sheet metal unit which may otherwise accompany the .processduring the inflation step especially in the area I containing the large cavity.

A heat exchange unit in accordance with a preferred.

embodiment illustrative of the invention is shown in FIG- URES 1, 2 and 3 of the drawing. The unit is fabricated as a single sheet metal plate 1 having erected. from a.

stratum of weld preventing material inits interior a system of fluid passageways by fluid pressure inflation. The system consists, in general, of relatively narrow,.long passageways delineated by the walls 2 and 3 protruding out of the plane, of plate 1 andthe relatively wide voluminous accumulator or boiler delineated by walls 4 and 5 ,also erected by inflation to. protrude out of the plane of platel;

Edge. openings and 16 form the inlet and outletof the conduit system. The narrow passageways include an entrance connection 6 anda discharge connection 7 for is placed between them alsoj 'in' -superpos'edj relationship.

the boiler cavity between the boiler walls 4 and 5 which.

are more separated by fluid pressure inflation than .walls 2 and'31in order to obtain a larger volume in series with the passageways. It is to be understood that the flat-like boiler of relatively large expanse, as compared to any one of the narrow. passageways, may be inflated to the same height as the passageways. In any event, theboiler walls 4 and 5 are internally braced by stays 9 audit carried :by'the inner or interleaved sheet 8. Stays9 are welded integrally with boiler wall 4: and stays 10 in turn are welded integrally with boiler Wall 5,all' without the use of solder for brazing material of any kind whatsoever. Stays'9, for instance, are joined to wall 4 at points 11 by a pressure weld.v Similarly, stays 10 :are joined or welded it points 12 to wall 5 by a type of joint which has a strength 'at 'least as, great as that of the parent metal or the stays and walls. However the boiler is not divided into, two

separate cavities by the intermediate sheet since 'it is provid'ed with perforations 13 at the places Where stays 9 have beenraised out of the sheet 8 and also perforations 14 at the places where stays 10 have been depressed out of sheet 8b}! the inflation operation. The internal structure between outer walls 4 and 5 of the boiler is shown best inFIGURE 2 and at the part of outer wall 4 broken away. in FIGURE :1. Y 7

It'willibe noted that the pressure welded largevolume cavity defined by walls4 and 5 is of a construction :which enables walls 4 andSto be erected by inflation to a more nearly flat configuration even without the aid of confinei t ment between fiat faced spaced press platens and 'at higher inflation .fiuid pressureswithless danger-of rupture. 1 Fur.- V thermore, this construction provides. stay members 9 and,

It) for holding boilerywalls: 4 and Sin position-without undue interference with fluid circulation within theicavityi In fact, the stay. structure, consisting ofmember-s 8, 9 and -10,'assist not onlyfinretaining the, outerfwallsA and 5 under high operating internaltpressurebut also inimproving the heat transfer characteristicsof the cavity structure. Another advantage of this structure'is that on accountof" the open framework which remains from; interinedlate sheet 8 after stay-s '9 and it? have been .li fted out: 'of* it, there is less contra-ction and resultant distortionln the plate -1'at the large cavity at walls 4 and 5.? As centre 5 readily Seen this construction provides a unit hav ng a series of three portions ofthe inner, sheet 8 disposed indifferent part-s and spaced relationship. For example, thegabovey identified 1open framework which is formed from lnterr: mediate sheet 8, co'nstit-rites'afirst portion: of, the shee v retained .in the original plane thereofwhereasin other parts of this-sheet a second ,portiondslifted out fmto stay 9 to project out of one face of thisinner'sheet S, and in addition ,athir-d portion of sheet-8i is lifted outof it into stay it) which projects from-the opposite face of this innersheet 8; -As a result this inner sheet 'is comprised of a plurality of loops which, project from opposite sides- 0f this memberwith the crest of'eachv of the loops ntegrated,

as by welding, withone 0f the .-Wall 4 andS adjacent thereto. Manufacture of a sheet metal unit in accordance with thi-s .invention.will be described in connection-With j FIGURES .4 and 5. e

The sheet metalunitismadeirofcornponent sheets 17,; f j 18 and 19, -as.=shown in FIGURE'A in peeled-back lposmon at oneend,-'%the better to illustrate the details of construction. Outer sheets 17 and 13lareplacedjtogether in SllPfiI."

position and in contact except where interleaved sheet 19 All three of the sheets"17,18 and 19, thus superposed,'are fastened together in any suitable manner as by meansof a pair of spottwelds, each one of whichjis located near th lateral edges of the preliminary assembly so as to prevent sliding or slipping action between the componentsheets.

Thus arranged,ithe assembly of "fastened components'fis heated to a suitable rolling temperature and then delivered to a rolling mill for suitable reduction for the accor'nplish-; ment of apressure weld between'ithe'.sheet-sfexcept at 'those interfacial areas where swan preventing material such as colloidal graphite has been-applied in .accordancewith j v a foreshortencd pattern which uponrolling: is elongated to predetermined dimensions". The pressure welded; plate formed by this procedure is then subjected, iusual-lyjaft'er annealing, to inflationbyrfl'uid pressure inI-order'to erect from the .bodyof theisingleplateifluid.passagewaysin accordance with a predetermineddesign asdelineate'dbY the position anddimensions of'the pattern of elongated 1.

weld preventing material;

in the rolling direction But it is to be understood that all the incisions'may extend, at an angle such as 45 with the rollingdirection.v Pairs'26 and 27 and pairs'28 iand'29' are arranged in rows and columns in sheet-19; and pairs 26 and 27,. alternate with pairs 28 and 29, in either direction.

The arrangement.ofslitsris jdisposed in sheetglfi inwardly 7 from the, edges 20, 21,124 and 25. Sheet 19yalso carries weld preventingmaterial applied iinja layer 30"to oneof the faces to bejuxtaposed adjacent v.to outer sheet: 18 and also weld preventing material in layer 31 applied to'the',

opposite 'face' to bejuxtapOsed, adjacent outer sheet 17:

Each layer of weld preventing material, which may con sist of any suitable composition and preferably one containing colloidal graphite, is applied in a pattern characterized by openings or islands free from weld preventing material. In layer 34B the islands 32 occur at the midsection between each pair of incisions 26 and 27 preferably spaced inwardly from the incisions, as is shown in FIG- URE 5. In layer 31 the islands 33 occur at the midsection between each pair of incisions 23 and29, preferably spaced inwardly from the incisions. This pattern of weld preventing material permits sheet 19 after passage through the pressure welding rolls to be welded to outer sheet 18 at the islands 32. Similarly upon passage through the pressure welding rolls, sheet 19 is welded to outer sheet 17 at the islands 33. Inasmuch as peripheral areas of sheet 19 along its edges 29, 21, 24 and 25, except for the entrance and discharge portions 6 and 7, are free from weld preventing material, pressure welding produces in the embryonic large cavity section, as defined by sheets 17, 18 and 19, a large internal parted area at which welding does not occur except at the relatively small islands 32 and 33. As is evident from FIGURE 5, these islands are arranged in rows and columns laterally and longitudinally spaced so the areas 32 on one side of the intermediate sheet 19 do not overlap with the areas 33 on the other side.

In accordance with the degree of reduction by rolling required, the dimension of intermediate sheet 19 between edges 20 and 21 is foreshortened and similarly the distance between incisions 26 and 27 is foreshortened as compared with the separation between incisions 28 and 29. As a result of foreshortening, the length of incisions 28 and 29 is initially and correspondingly less than the length of incisions 26 and 27. To avoid distortion in the form of buckling and rippling, lateral edges 2-5, 25 and 43 of sheets 17, 19 and 18, respectively, are in coincidence and similarly, lateral edges 44, 24 and 42 of sheets 17, 19 and 18, respectively, are in coincidence.

it will be understood that where the roll spacing of the rolling mill is fixed the amount of reduction at the three layer portion of the assembly will be greater than the amount of reduction at the two layer portion. However, if desired, the roll separation or bight may be adjusted so as to give a substantially uniform degree of metal reduction over the entire sheet metal unit to leave a thickened portion at the three layer boiler part of the sheet metal unit. This latter procedure provides the added advantage of thickened boiler walls 4 and 5. Where the roll spacing is fixed there is obtained in the boiler area the advantage of more severely worked metal amenable to softening by annealing more quickly and completely at lower temperatures. This provides metal, such as walls 4 and 5, more easily inflated in the boiler area than in the other areas. With such working and with the strap structure herein described, inflation to final form can be done without confinement in a die or press. Alternately, inflation may occur with confinement between dies or flat face platens only in the boiler area while the narrow work hardened passageways may be inflated free without any need for their walls 2. and 3, FIGURES l and 3, to be in contact with the more widely spaced die faces contacting boiler walls 4 and 5. Other variations of the rolling and inflation procedures may suggest themselves to those skilled in the art.

In the modified intermediate sheet 34 shown in FIG- URE 6, incisions 35 run parallel to each other across the width of the sheet and extend in the direction of rolling terminating short of the leading and trailing edges so as to leave marginal connecting portion 36 at the leading edge and marginal connecting portion 37 at the trailing edge inwardly from the periphery of sheet 34. Each face is then coated with a longitudinally foreshortened pattern of weld preventing material such as layer 38 on the top face and layer 39 on the bottom face. Weld preventing layers 38 and 39 are in coincidence and identical except for the islands 40 and 41 free from weld preventing material. The weld preventing material free areas 40 of the top layer 38 alternate and do not overlap with the weld preventing material free areas 41 of the bottom layer 3h. It is evident that with sheet 34 interposed between outside component sheets 17 and 18 in the proposed boiler in lieu of sheet 19 of FIGURE 4, pressure welding by rolling will cause weld preventing material free areas 48 to integrate with one of the outside component sheets while weld prevent ing material free areas 41 integrate with the other outside sheet. Upon injection of inflation pressure to the interior of the resultant pressure welded sheet metal unit there is formed a system of stays within the boiler of a form having a diiferent configuration than that shown in FIGURE 2 but otherwise similar in principle.

The intermediate or interleaved sheet may be thicker or thinner than the outside component sheets. It is also to be understood that the intermediate sheet may be coextensive with the outside component sheets particularly where the large volume cavity takes up the greater part of the area of the sheet metal unit. It is also quite obvious that the layers of weld preventing material may be applied to the outside sheets rather than to the intermediate sheets.

It will be appreciated that by means of this invention there is provided a heat exchange element or other hollow sheet metal unit having a thin-walled cavity of large fluid capacity reduced only slightly by the presence of the internal straps. These serve as heat transfer elements and also as stay bars or straps for preventing excessive outward distortion of the walls of said cavity under high internal pressure of a working fluid medium. These internal straps are cold worked by the inflation operation and are thereby strengthened.

Since many other embodiments of this invention may occur to those skilled in the art, it is to be understood the foregoing is intended by way of illustration of a preferred embodiment and not as a limitation of the scope of the present invention except as set forth in the appended claims.

What I claim is:

1. In a sheet metal unit, a voluminous thin-Walled cavity of large expanse defined between substantially superposed planar outer Wall members disposed in spaced relationship to each other, and a single inner wall member subdividing said cavity and welded to said outer wall members along spaced marginal portions of the adjacent faces of all said members, said inner wall member being coextensive with said outer wall members between said marginal portions and disposed between and partially lying in a plane in spaced relationship to said outer wall members with said inner wall member having between said marginal portions a first portion, a second portion, and a third portion disposed in diiferent parts of said inner wall member, with all of said first portion comprising a first perforation through said member and a first strip of said inner wall member bowed out therefrom in superposed relationship with said first perforation and extending as a first loop projecting out from one of the opposite faces of said inner wall member with the crest of said first loop integrated with one of said outer wall members adjacent said one face, said second portion being spaced from said first portion and comprising a second perforation through said member and a second strip of said inner wall member bowed out in superposed relationship with said second perforation and extending as a second loop projecting out from the other of said faces with the crest of said second loop integrated with the other of said outer wall members adjacent said other face, and said third portion disposed in the normal plane of said inner wall member in its spaced relationship with said members.

2. In a sheet metal pressure welded unit a voluminous thin-walled cavity of large expanse defined between substantially superposed planar, outer wall members disposed in spaced relationship to each other and ,asingleiinner 'wall member subdividing 'said cavity'and welded to said 'outer, wall members along spaced n'iargirial portions ofthe adjacent faces of all said members, said inner Wall meme her being coextensive withlsaid outer wall members be- 1 tween said,marginal portions and disposed between and partially lyingin a plane in spaced relationship ,to said outer wall members with said inner wall member: having between said marginal portions a first portion, a second portion, and a third portion, disposed in different parts 'of said inner-wall member, with all of said first portion comprised of a strip of saidinner wall member projecting frorn'out of one of theopposite faces of said inner Wall as a loop with the crest of said loop integratedwith;

the outer wall member 'adjacentsaid one ,face, said second portion spaced from said first portion and comprising a second strip of metal projecting as aloop from the other of said opposite faces with the crest of the la'stsaid loop integrated with the other of said outer wall members adjacent said'other face, and said third portion disposed in the normal plane of said inner wall member in its spaced relationship with said members.

3. In anintegrated sheetmetal unit, a voluminous thin 'Walled cavity of large expanse defined between outer wall members disposed in spaced relationship Witheach other, a single inner wall subdividing said cavity and welded along spaced marginal portions of each of its faces to an adjacent outer wall member,;said inner wall between'said margina l portions being co-extensive with said, wall meme bers and partially lying in a plane in spaced relationship to said wall "members with-said inner wallcomprisedof a first portioma secondportion and a third portion disposed in different parts of said inner wall with all of said first portion'comprising a first perforation through said inner wall andafirst' loop of said inner wall disposed in superposed relationship with said first perforation andv projecting out from one of the opposite faces ofsaidinner Wall with the crest of said strip integrated withone of said wall members adjacent said one face, said second portion being spaced from said first portion and comprising a secondperforation through, said inner wall and a second loop of said inner wall disposed in superposed relationshipwith said secondzperforation1 and projecting "out of theother'of said, faceswith the crest of said second "loop integrated with "the other of -said rzwall members, and 'saidthird; portion disposed in {the normal plane ofsaid 4. ;An' integrated sh eet metal uni t1 comprised of'gt'wo 5 -inner wall'in.itsjsaid;spaced relationship :witlrsaid wall' superposed and spaced ,outerwall membersand aisiugle 1 inner wall member disposedbtween and partially lying in a plane, in spaced relationshipto said'fme'rnbersiwith said member havingportions thereof partially severed and bowed out of the plane, of said'member into loops projecting from oppositesides 'ofsaid member withIthe priest, of one: of saidloops which iprojectsout Qfftlle oppo- 15 site faces of said :member :integrate'dwwith'one of said members adjacent said 'onewface ,and. with the CISt 'Qf a second of said loops whichprojects; out 'of the other of said faces integrated to theother of said.members,adv

jacent saidjother face, all 'ofssaid first loops having'a 20, longitudinal extentina firstdirection-and-all 'ofs'aid second loopshaving a longitudinal ,extentin a SQCOllddlIGQ',

,tion which issubstantially perpendicular. to said first,

' direction, and a'portion of saidl'mernb erremaining'infthei normal plane of i said memberin its spaced relationship,

first and second loops;

References Zitedjhy thelExaminerz U ITED, srA'rEsrArE Ts 514,313

rrERMA BERM-A 'HERBERTL; ARTIN,5P'ERCY L. PATRICKZIExa'miners; i Q

from said members and integrally connectedfwithffsaid 

1. IN A SHEET METAL UNIT, A VOLUMINOUS THIN-WALLED CAVITY OF LARGE EXPANSE DEFINED BETWEEN SUBSTANTIALLY SUPERPOSED PLANER OUTER WALL MEMBERS DISPOSED IN SPACED RELATIONSHIP TO EACH OTHER, AND A SINGLE INNER WALL MEMBER SUBDIVIDING SAID CAVITY AND WELDED TO SAID OUTER WALL MEMBERS ALONG SPACED MARGINAL PORTIONS OF THE ADJACENT FACES OF ALL SAID MEMBERS, SAID INNER WALL MEMBER BEING COEXTENSIVE WITH SAID OUTER WALL MEMBERS BETWEEN SAID MARGINAL PORTIONS AND DISPOSED BETWEEN AND PARTIALLY LYING IN A PLANE IN SPACED RELATIONSHIP TO SAID OUTER WALL MEMBERS WITH SAID INNERR WALL MEMBER HAVIN BETWEEN SAID MARGINAL PORTIONS A FIRST PORTION, A SECOND PORTION, AND A THIRD PORTION DISPOSED IN DIFFERENT PARTS OF SAID INNER WALL MEMBER, WITH ALL OF SAID FIRST PORTION COMPRISING A FIRST PERFORATION THROUGH SAID MEMBER AND A FIRST STRIP OF SAID INNER WALL MEMBER BOWED OUT THERE- 